Hugs, it's hard when they are poor sleepers
think your not doing things right
Please there is no "right" or "wrong" - loving your baby is always right.
Some babies struggle to sleep longer times & at 2/3/4mo its' surprisingly common to get short sleep cycles.
Firstly I'd work on what gives you the most sleep & to a degree try not to worry about your little one & relax.
If you want 9am to 9pm then make sure that there is only feeds that is "awake" time & the rest of the time is quiet, dark & low key. If your lo is sleeping well on you & you can't try to limit that. I found I got really bad insomnia with my DS1 & so had to learn some relaxation strategies to help. In recent years I've found taking Magnesium supplements helps too... definitely look at sleep vitamins if you are struggling, they really can help.
In terms of what to do first or what is most important, that depends on what you can deal with & what you find will mentally help you the most. For me night sleep was always my most important part & so I'd try that first, esp as at her age short naps are more normal than not.
Also be mindful that there is a growth spurt around 3mo (my youngest also at 41 weeker) hit his around the 10.5 week mark, so if you are BF then that will add into the mix, so feeding more can help.